Automatic Identification and Tracking of Sunspots

Charlotte Proverbs

Hosted by University of Central Lancashire, United Kingdom on June 13, 2024

Abstract

It is well understood that the dynamics of sunspots lead to energy being transferred to the solar atmosphere and stored in the coronal magnetic field. This provides a surplus of energy that may be released in solar eruptions. The driving mechanisms for this energy transfer may include sunspot rotations, both within individual sunspots and between sunspot pairs. Calculation of the rotations of individual sunspots have been carried out by several authors, but studies of the rotation of sunspot pairs has been less systematically investigated.

Calculation of rotations in either case rely on careful tracking of the sunspots from observation to observation. Identification and tracking of sunspots is therefore essential to understanding the energies in play that lead up to solar eruptions. To date, this has predominantly been done manually which has restricted many studies to being a small number of case studies rather than large statistical samples. In order to construct large samples, the careful tracking of sunspots must be automated.

We present a fully automatic method to identify and track sunspots in long sequences of data from the Solar Dynamics Observatory Helioseismic and Magnetic Imager (SDO/HMI) at a high temporal resolution. This includes registering the splitting and merging of sunspots, and allocating sunspots to active regions. This information can be fed into algorithms to measure the rotation of individual sunspots or used to calculate the relative motion of sunspots with respect to each other (including co-rotation).

The method is applied to a four-month data set that has previously been analysed using a semi-automatic method where the basic sunspots were identified by eye, and the results are compared to determine any differences between the methods. From this data, sunspot dynamics such as sunspot rotation, shearing and merging are calculated, alongside sunspot pair interactions. Case studies of successfully tracked sunspots will be presented, showing examples of the individual sunspot rotations and some initial results involving sunspot pair interactions with correlations to solar activity.